Primary sources, usually referred to as primary research articles, are reports of original experiments or observations conducted by scientists. Primary research articles are published in peer-reviewed academic (or scholarly) journals such as Cell Biology and Nature.
Secondary sources provide analysis, commentary or interpretation of work done by others. Secondary sources often summarize the general information of what is known on a specific topic. Textbooks, review articles, videos and news articles are all secondary sources. Wikipedia, like other encyclopedias and reference works, is a secondary source.